An intriguing mystery and a threat to San Francisco PI Sabina Carpenter’s career drive Muller and Pronzini’s engaging second late-19th-century historical starring her and partner John Quincannon (after The Bughouse Affair). The wealthy parents of 18-year-old Virginia St. Ives, fearing she’ll fall prey to an unsuitable fortune-hunter, have hired Sabina to keep an eye on their daughter. When Virginia gives her the slip at a debutante ball, Sabina tracks the heiress through the fog, only to see her leap from an overlook to certain death hundreds of feet below. Oddly, searches of the area where she was seen to fall fail to turn up a corpse. Virginia’s father threatens to sue Sabina for negligence if his daughter is proven to have committed suicide. Quincannon, meanwhile, is hoping to land a lucrative reward by tracking down a bank thief. While the solution to the St. Ives mystery isn’t the cleverest MWA grand masters Muller and Pronzini have ever devised, it will leave readers satisfied. Agent: Dominick Abel, Dominick Abel Literary Agency. (Dec.)